The improvement in the level of integration of semiconductor devices, and thus, development in fabrication design techniques thereof have brought about a number of efforts to realize a semiconductor system on a single chip. Such a single chip system has been developed, based on technology to integrate controllers, memories and circuits operating at low voltages into a single chip.
However, to realize low weight and miniaturization of a semiconductor system, it is necessary to integrate a circuit part to control power of the system, i.e., input and output terminals and main functional circuits into a single chip. However, input and output terminals cannot be realized as a low-voltage CMOS circuit, because high voltages are applied thereto. Accordingly, these terminals are generally realized by high-voltage power transistors.
Accordingly, to reduce the size and weight of systems, input/output terminals of a power source and a controller should be integrated into a single chip. A technology to realize this integration is a power IC, which includes a high-voltage transistor circuit and a low-voltage CMOS transistor circuit integrated into a single chip. Such a power IC technology is an improvement of a vertical DMOS (VDMOS) device as a discrete power transistor, which may realize a lateral DMOS (LDMOS) device. In an LDMOS device, a drain is laterally arranged to allow current to laterally flow and a drift region is interposed between a channel and the drain to assure high breakdown voltage.